How to make jagged geometry smooth/diagonal?
This is a bad topology with high poly count and work with this becomes hard and more inefficient.

You will need to adjust many things manually because the tools works based on topology of your mesh and if it has a bad topology, then, the tools have bad results too:

But using the Relax tool from the Loop Tools addon maybe you can solve your problem:

Loop Tools addon already inside in blender and to enable it go to Edit > Preferences > Addons and search for "loopTools"


Now you can use the Relax tool:


N panel > Edit > LoopTools > Relax